1. Field of the Invention
This invention relates to retubing shell and tube heat exchangers, such as nuclear steam generators, and more particularly, to a dual duty tube guide and tube expander apparatus which is tapered to facilitate tube insertion and is compatible with a tool which engages the apparatus, actuates the apparatus's tube expansion feature, and extracts the apparatus from the tube.
2. Description of the Prior Art
Tapered tube guides, releasably retained in the leading end of heat exchanger tubes for guiding those tubes through aligned apertures in spatially separated support plates and ultimately into proper position within tube sheet apertures are well known in the art. Conical nosed tube guides were, according to the prior art, removed upon proper tube-to-tube sheet positioning so as to permit a subsequent tube-to-tube sheet connection. Such connections are customarily obtained by roll-expanding or welding the tube to the tube sheet. However, even in the case of welding, the tube is often "tack-rolled" into place in preparation for the final seal welding of the tube-to-tube sheet.
Conical nosed tube guides having bristles projecting from a central stem in a spiral configuration and an apparatus for extracting those tube guides from tubes in which those guides are releasably retained are specifically described in commonly assigned, copending application Ser. No. 898,348 filed Apr. 21, 1978. While removal of such tube guides from the tubes would normally be performed manually by workmen from the inside of a channel head on the primary side of the tube sheet, in the case of a shell and tube heat exchanger which has been exposed to a hazardous environment such as the radioactivity found in a nuclear steam generator, it is desirable to effect any repair or replacement operation thereto through remotely operated mechanisms to minimize exposure of workmen to the radioactivity.
The aforementioned copending actuator-extraction apparatus cooperates with a support-positioning apparatus described in commonly assigned copending patent application Ser. No. 888,701 filed Mar. 21, 1978. Such support positioning apparatus is designed to operate within a steam generator's channel head while being controlled from a remote location which is suitably shielded from the channel head's radioactive environment. While the apparatus described in Ser. No. 898,348 permits automated, remote extraction of tube guides, it is desirable to have a tube guide and extraction tool for use therewith that will not only automatically extract the guides from the tubes and release them upon their extraction, but also expand or tack-roll the tube into contact with the tube sheet's aperture in preparation for the subsequent seal weld therebetween.